[OSM-talk] OSM on Mobile Phones (and beyond!)

Steve Bromwich osm at fop.ns.ca
Tue Jul 3 18:23:46 BST 2007


On Mon, 2 Jul 2007, tim wrote:

> In preparation for my talk at SOTM on "OSM on Your Phone", I'd like to
> know if you've come across, used, or have thoughts on Openstreetmap
> with mobile phones.

Treo 650 with both Lowrance iFinder (NMEA through serial cable) and a 
BGT-11 (NMEA over Bluetooth). CetusGPS and CotoGPS are reasonably good but 
with their flaws (Cetus is a pain to delete previous points, for example). 
For mapping, I've been experimenting with Pathaway GPS 
(http://www.pathaway.com/) and managed to figure out a rather tedious way 
to get maps into it that aren't so large they won't fit on my Treo:

1. Use the osm2ozi_tah.pl app (see 
http://wiki.openstreetmap.org/index.php/Oziexplorer) to generate the map 
and calibration files, like so:

./osm2ozi_tah.pl  -tilename="11,661,739" -tilesource="http://dev.openstreetmap.org/~ojw/Tiles/tile.php"

2. Next, reduce the image to monochrome. Load the image into Gimp, and 
click Image, Mode, Indexed and check "Use black and white (1-bit) palette" 
and set "Color dithering" to "Floyd-Steinberg (reduced color bleeding)". 
Save the image as the same filename (otherwise the calibration file will 
be wrong).

3. Load the resulting image into the Pathaway Map Manager (runs fine under 
Wine):

File, Import New Map, select the file you just saved, set Color Depth to 
1-bit (BW), check Compressed, click OK.

It will now grind through the image while it converts it from 1 bit to 1 
bit again. Unfortunately the algorithm used in Pathaway is somewhat 
lacking, so if full colour images are used the dithering goes wonky - or 
it creates a huge map file. Once it's done, the image needs to be 
calibrated:

Click Calibration, Calibration type Lat/Long (rectangular), Coordinate 
type top left and bottom right (ignore any popup messages about losing 
current calibration), the lat/lon fields should magically autopopulate.

Click File, Save Pathaway Map, save the map (as a prc for Palm - not sure 
about Wince).

I tried Trekbuddy but it didn't seem to want to work with the IBM JVM for 
Palm. I vaguely recall hearing of a freeware app that did calibration of 
raster images, but I can't recall enough detail to turn up anything useful 
in Google - if this rings a bell with anyone else I'd be interested as I'm 
sure the general principle of osm2ozi_tah can be extended to other 
formats...

> For example, in addition to collecting gpx traces and displaying
> rendered maps, I could have osm data editing on-the-fly as I walk down
> the road. Also, I'm thinking it would be great to be able to tell if,
> when I'm on a street/area, if that street/area has already been mapped
> via text.....

This method lets me see what's been mapped up to the point the map was 
created, I can see how updating on the fly would be nice. The only problem 
is graphics - I stuck Google Maps on my Treo and thought it was quite 
nifty to wander around mapping on the Treo, until I saw the megs and megs 
of data that were downloaded - on a 10 meg data plan, that was most of the 
month gone in 20 minutes!

Cheers, Steve




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